With advancements in miniaturization of semiconductor integrated circuits, for example, manufacturing using an EUV (Extreme Ultra-Violet) exposure apparatus which uses a wavelength shorter than that used in an ArF exposure apparatus has been studied to manufacture micro circuits with a circuit line width of less than 40 nm. An EUV light source with a center wavelength of 13.5 nm has also been developed. For the EUV exposure apparatus, there is no appropriate lens material (high transmittance, high refractive index difference) for forming a dioptric system, and the transmittance in the air is bad, so it is necessary to use reflective optics and a reflective mask in vacuum.
Further, there is no single layer material having a high reflectance with respect to an EUV wavelength. Therefore, reflectance of all reflection mirrors and a mask used in EUV exposure are improved by forming a multilayer film made of at least two types of different materials (for example, Mo, Si, and the like) satisfying Bragg reflection condition on the surfaces thereof.
However, in the EUV exposure, a maximum reflectance of the reflection mirrors is about 70% per reflection mirror. Therefore, considering the number of reflection mirrors required in an EUV optical system (for example, about 15 reflection mirrors), a ratio of an amount of light irradiated onto a wafer to an amount of initial EUV light is (0.7)^15=0.47%. Thus, how to increase an output of light source and how to improve light transmission efficiency are important technical objects.
There are a discharge produced plasma type EUV light source and a laser produced plasma type EUV light source. As plasma species, Xe, Sn, or the like are used. Besides the EUV light, light with various wavelengths (so called “outband” components) is generated from plasma. There is little chromatic dispersion in reflective optics, so an amount of light attenuated by reflectance corresponding to each wavelength reaches a mask and a wafer. An EUV resist has photosensitive characteristics for a DUV (Deep Ultra Violet) wavelength (100 nm to 299 nm), so there is concern that DUV light affects pattern transfer characteristics.
As one of methods for highly accurately evaluating how outband components such as DUV light are distributed in an exposure area, there is a method in which a light amount monitor for measuring DUV light is mounted on a wafer stage or a mask stage. However, when using this method, configuration of the apparatus is complicated and it takes time and effort to measure the DUV light. Therefore, it is desired that outband components such as DUV light are easily evaluated.